What Is an Unhappy Triad?

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  • Written By: Christina Edwards
  • Edited By: W. Everett
  • Last Modified Date: 19 January 2020
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A blown knee is known by several different names, including terrible triad, O'Donaghue's triad, and unhappy triad. This is a common sports injury that generally damages three major components in the knee. Signs of an unhappy triad include a pop, pain, and instability. Surgery is usually necessary to repair the damage.

An unhappy triad is a common injury in many sports, especially contact sports. American football players, who are tackled and hit often, are especially susceptible to this type of injury. This often occurs when an athlete's knee is struck as his foot is firmly on the ground while turning.

Three major components of the knee are damaged in an unhappy triad. The anterior cruciate ligament and the medial collateral ligament are two of the major ligaments located on the inside of the knee, and these are partially responsible for stability. The medial meniscus is a disc consisting of fibrocartilage, also located inside the knee. This acts as a shock-absorbing cushion when a person walks or runs.

Either of these ligaments can tear, or snap, completely during this type of injury. The meniscus often tears. This damage can create several symptoms.


Often, a patient suffering from an unhappy triad will hear a loud pop at the time of the injury. Because of the extent of the injury, there will also be a great deal of pain. The sufferer will also be very unstable and unable to stand of the affected knee. Along with these symptoms, there will also be swelling and, sometimes, bruising in the area.

The recommended first aid for an unhappy triad is rest, ice, compression, and elevation (RICE). The knee should be rested, or immobilized, and ice should then be applied, which will help alleviate swelling. The area should also be compressed, by wrapping it with an elastic bandage, and elevated above the level of the heart. These measures can also help stop swelling in the area.

Serious knee injuries, like an unhappy triad, should be evaluated by a medical professional as soon as possible. Most patients with this injury will usually need surgery for their knees to heal. After this injury, the anterior cruciate ligament and the medial meniscus will usually need to be repaired, or reconstructed. Sometimes, depending on the extent of the injury, the medial collateral ligament may also need to be repaired, but this will often heal on its own after a time.

Recovery after an unhappy triad is usually quite long. It will sometimes take almost a year before a patient's knee is fully recovered. Physical therapy and regular, safe exercise can help speed this process along.



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